Syngas conversion process

ABSTRACT

A process for converting syngas to a hydrocarbon product comprising at least 20 percent oxygenated hydrocarbons which process comprises contacting the syngas with a catalyst comprising ruthenium metal on a faujasite type of zeolite which is subsequently treated with a borane solution and calcined under special conditions is disclosed herein.

FIELD OF THE INVENTION

This invention relates to a process for converting syngas tohydrocarbons having a substantial proportion of oxygenated hydrocarbonsutilizing a ruthenium-based catalyst.

BACKGROUND OF THE INVENTION

In an integrated coal gasification unit it is useful to be able toconvert the syngas to a variety of products such as alkanes, olefins,aromatics and oxygenated hydrocarbons and subsequently separating outthe various compounds, such as the oxygenates, like alcohols andaldehydes, and utilizing these materials for their own use, such as forsolvents, or as starting materials to prepare other useful chemicalcompounds.

SUMMARY OF THE INVENTION

The instant invention relates to a process for converting syngas to ahydrocarbon product which comprises at least 20 percent oxygenatedhydrocarbons which process comprises contacting the syngas with acatalyst composition prepared by ion exchanging a ruthenium-containingsolution with a faujasite type zeolite, calcining and then reducing theruthenium-containing zeolite, subsequently contacting theruthenium-containing zeolite with borane, and subsequently calcining innitrogen and then reducing the borane-treated material. The use ofcatalyst compositions prepared in this fashion provides a higherconcentration of oxygenates in the product than does the use ofconventional supported ruthenium catalysts. The instant catalysts alsodiffer significantly from similar catalysts described in applicants'copending application Ser. No. 410,297, filed Aug. 23, 1982, wherein thecatalyst is calcined in air rather than nitrogen just prior to the finalreduction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The instant invention comprises a process for converting a mixture ofcarbon monoxide and hydrogen (syngas) to a hydrocarbon product whichcomprises at least 20 and preferably 30 percent by weight of oxygenatedhydrocarbons which process comprises contacting the syngas with acatalyst composition prepared by:

a. ion-exchanging the sodium ions of the sodium form of a faujasite typezeolite with ruthenium ions by contacting said zeolite with a solutioncontaining a soluble ruthenium compound,

b. calcining the ruthenium exchanged zeolite in nitrogen at atemperature ranging from about 300° C. to about 600° C.

c. contacting the ruthenium-containing zeolite with hydrogen at atemperature ranging from about 300° C. to about 600° C. whereby theruthenium is reduced to the metal,

d. contacting the ruthenium metal-containing zeolite with a solution ofborane,

e. calcining the borane-treated zeolite in nitrogen at a temperatureranging from about 300° C. to about 600° C. and then

f. contacting the borane-treated zeolite with hydrogen at a temperatureranging from about 300° C. to about 600° C.

The zeolite used to prepare the catalysts used in the instant inventionis of the faujasite type and is utilized initially in the sodium form,that is, the various exchange sites are satisfied by sodium. Suchzeolites are described in U.S. Pat. Nos. 2,882,244, usually referred toas X zeolite and U.S. Pat. No. 3,216,789, referred to as a Y zeolite,and also in U.S. Pat. No. 3,446,727. These faujasitic type zeolites havebeen widely employed in catalytic processes such as for the conversionof hydrocarbons and are generally well known. The patent and generalliterature are extensive on these. In preparing the instantcompositions, the sodium form of the faujasite type zeolite is contactedwith a solution of a ruthenium salt whereby the ruthenium ion ision-exchanged with the sodium ion. Any suitable, soluble ruthenium saltcan be utilized, dissolved in an appropriate solvent. Suitable salts andsolvents are readily determined by one skilled in the art. Illustrativeexamples of suitable ruthenium salts include salts such as ruthenium(III) chloride hydrate, ruthenium (III) bromide, anhydrous ruthenium(III) chloride and ruthenium nitrate. Also suitable are the ammoniacomplexes of the ruthenium halide such as, for example, Ru(NH₃)₆ Cl₃ andRu(NH₃)₆ I₃. Salts of suitable organic acids are also suitable. Here,examples include ruthenium (III) acetate, ruthenium (III) propionate,ruthenium hexafluoracetylacetonate, ruthenium (III) triofluoracetate,ruthenium octanoate, ruthenium naphthenate, ruthenium valerate, andruthenium (III) acetylacetoneate.

Suitable solvents for the desired ruthenium compounds can readily bedetermined by simple experimentation. Preferred solvents are water andthe lower alkanols. After contacting the sodium form of the zeolite withthe ruthenium-containing solution, the ruthenium-exchanged zeolite isdried and then calcined in nitrogen at a temperature ranging from about300° C. to about 600° C. Calcination times are not critical and rangefrom about 0.1 to about 20 hours. After calcination, theruthenium-containing zeolite is reduced in a hydrogen atmosphere at atemperature ranging from about 300° C. to about 600° C. The reactiontime is not critical but is adjusted according to the temperature ofreduction, higher reduction temperatures will require shorter times andvice versa. Generally, times range from about 0.1 to about 20 hours. Thereduction conditions are chosen, such as to reduce the ruthenium whichis an ionic form in the zeolite to ruthenium metal which will bedeposited on the surfaces (external and pore volume) of the zeolite.

The ruthenium metal-containing zeolite is then contacted with a solutionof borane (BH₃ or diborane B₂ H₆) in a suitable organic solvent.Suitable solvents comprise the ether solvents, particularly suitable istetrahydrofuran. The borane is typically prepared by the reaction of ametal hydride with a boron halide in an ether-type solvent. The boranecompounds are sensitive to both air and moisture, so the above mentionedimpregnation of the zeolite with the borane compound must be maintainedunder anhydrous, air-free conditions.

After the zeolite has been impregnated with the borane solution, it isdried at relatively low temperatures up to about 50° C., and thencalcined in nitrogen at a temperature ranging from about 300° C. toabout 600° C. The calcined borane-treated zeolite is then reduced in ahydrogen atmosphere at a temperature ranging from about 300° C. to about600° C. Calcination and reduction times are not critical and range fromabout 0.1 to about 20 hours.

The resultant catalytic material is used in a fashion typical of thatutilized for heterogeneous catalysts. It may be used in fixed beds, influidized beds or in batch reactors. Typical reaction temperatures rangefrom about 175° C. to about 350° C., preferably from about 200° C. toabout 300° C. Typical reaction pressures range from about 5 to about 500bar, preferably from about 5 to about 200 bar, and typical feed ratesinclude gaseous hourly space velocities ranging from about 500 to about10,000 1/1/hour. A wide range of carbon monoxide to hydrogen can be usedin the feed. For example, a CO:H₂ ratio ranging from about 1:2 to about3:1 is suitable.

The process of the instant invention, including preparation of thecatalyst composition, will be further described below by the followingillustrative embodiments which are provided for illustration and are notto be construed as limiting the invention.

ILLUSTRATIVE EMBODIMENTS Catalyst Preparation

The following example illustrates the typical preparation of acomposition falling within the scope of the instant invention. 30 Gramsof Ru(NH₃)₆ Cl₃ are dissolved in 150 cc of water and added to a 50 cccondensing flask. 60 Milliliters of the sodium form of Y zeolite(L24-52/RW Linde) was calcined for 24 hours at 500° C. and then added tothe reflux flask and refluxed for about two hours. The zeolite was thenfiltered and washed with approximately 500 cc of water. The zeolite wasthen placed in a quartz flow tube and calcined in a nitrogen flow (atabout 550° C. for five hours). The temperature was raised from roomtemperature to 550° C. at a rate of approximately 10° C. per minute.After calcining, the quartz flow tube was cooled and the hydrogen flowwas initiated through the tube. The temperature was then again raised toabout 500° C. at a rate of about 10° C. per minute. The material wasmaintained at 500° C. for about two hours. After reduction the samplewas cooled to room temperature. Twenty-five cubic centimeters of theruthenium-treated zeolite was contacted with 125 cc of a one molarsolution of BH₃ in tetrahydrofuran. The borane-treated material was thendried at about 40° C. on a rotovac dryer for about three hours. Thesample was then placed in a quartz tube, nitrogen flow was initiated andthe tube was heated at about 10° C. per minute to about 550° C. forabout five hours. After calcination the sample was cooled, hydrogen flowwas then initiated over the sample, and the sample was heated to about500° C. at a rate of about 10° per minute for about two hours. Afterthis reduction, the sample was cooled overnight. During the abovepreparative techniques, the sample was maintained under dry boxconditions except for the calcination and reduction process.

PROCESS Syngas Reaction

The catalyst composition, according to this invention (Example 1), wasprepared in the fashion described above. Analysis of this compositionshowed that it had approximately 6% w ruthenium and about 0.97% w boron.The sample was placed in a tubular flow reactor and heated to theappropriate reaction temperature as indicated in Table 1. Carbonmonoxide and hydrogen in a molar ratio of about 1:1 were fed to thereactor under the conditions indicated in Table 1. The products of thereactor were analyzed by gas chromatography, and the results are shownin Table 1 below. For comparative purposes, other compositions notfalling within the scope of this invention were prepared. Example Acomprises a ruthenium metal supported on a Y zeolite. This is basicallythe same as Example 1 without the borane treatment. Example B comprisesthe use of an alumina-silica as a support rather than a zeolite. Thealumina-silica is Davison 980-25 which has a similar Al/Si ratio as theY zeolite. This example was prepared in the same fashion as Example 1.Example C is substantially the same as Example B without the boranetreatment. Example D comprises a composition prepared according to theteachings of applicants' copending application Ser. No. 410,299, filedAug. 23, 1982, wherein just prior to the final reduction the compositionis calcined in air rather than nitrogen. Example D producessubstantially higher paraffins with carbon numbers around 30.

As can be seen from the table, the composition of the instant inventionprovides a much higher yield of oxygenates (alcohols and aldehydes) thanthe other comparative examples.

                                      TABLE 1                                     __________________________________________________________________________    SYNGAS CONVERSIONS BY RU/B/Y AND RELATED CATALYSTS                                     Example:                                                                           1    A   B       C     D                                                 Catalyst:                                                                          Ru/B/Y                                                                             Ru/Y                                                                              Ru/B/Al--Si*                                                                          Ru/Al--Si*                                                                          Ru/B/Y                                   __________________________________________________________________________    Ru (% w)      6.00 7.10                                                                              3.96    3.96  7.10                                     B (% w)       0.97 --  0.75    --    1.02                                     GHSV (1/1/hr) 4000 4000                                                                              3000    4000  4300                                     Temperature (°C.)                                                                     250  220                                                                               250     250   250                                     Pressure (psig)                                                                             1500 1800                                                                              1000    1500  1000-1500                                % Syngas (1:1) Conversion                                                                   6.4  5.1 11.5    2.8   15.5                                     Molar Selectivity %                                                           Overall In C.sub.5.sup.+                                                      C.sub.1                                                                           Methane   20.6 12.8                                                                              8.9     22.6  3.2                                          Methanol  3.8  0.6 --      0.78  0.4                                      C.sub.2                                                                           Ethylene/Ethane                                                                         2.4/--                                                                             4.0/0.6                                                                           2.4/0.6 7.1/--                                                                              1.5/--                                       Ethanol   1.8  --  --      --    --                                       C.sub.3                                                                           Propene/Propane                                                                         0.3/2.4                                                                            1.1/2.2                                                                            --/0.4  --/4.1                                                                             --/--                                        Propanol  --   --  --      --    --                                       C.sub.4                                                                           Butene/Butane                                                                           2.0/8.8                                                                              --/11.7                                                                         3.5/7.7  3.4/14.2                                                                            --/2.9                                      Butanol   --   --  --      --    --                                       C.sub.5.sup.+ 57.9 67.2                                                                              76.3    46.9  91.0                                         Paraffins 41.4 54.7                                                                              57.8    50.7  ↑                                      Olefins   16.4 31.0                                                                              34.2    31.2  ↑                                      Alcohols  24.6 5.5 1.4     10.6  about C.sup.30                               Aldehydes 11.9 3.2 2.3     6.7   paraffins                                    Paraffins 57.5 64.0                                                                              64.2    64.6  ↓                                     Olefins   14.2 25.7                                                                              31.9    25.1  ↓                                     Alcohols  19.8 4.4 1.1     5.8   ↓                                     Aldehydes 6.9  2.2 1.8     3.1   ↓                                 __________________________________________________________________________     *Davison 98025 aluminasilicate which has similar Al/Si ratio as Y zeolite                                                                              

I claim:
 1. A process for converting a mixture of hydrogen and carbon monoxide to a hydrocarbon product which comprises at least 20 percent oxygenated hydrocarbons which process comprises contacting the hydrogen and carbon monoxide at a temperature ranging from about 175° C. to about 350° C. and a pressure ranging from about 5 bar to about 500 bar with a catalyst composition prepared by a process which comprises:a. ion-exchanging the sodium ions of the sodium form of a faujasite type zeolite with ruthenium ions by contacting said zeolite with a solution containing a soluble ruthenium compound, b. calcining the ruthenium exchanged zeolite in nitrogen at a temperature ranging from about 300° C. to about 600° C., c. contacting the ruthenium-containing zeolite with hydrogen at a temperature ranging from about 300° C. to about 600° C. whereby the ruthenium is reduced to the metal, d. contacting the ruthenium metal-containing zeolite with a solution of borane, e. calcining the borane-treated zeolite in nitrogen at a temperature ranging from about 300° C. to about 600° C. andthen f. contacting the borane-treated zeolite with hydrogen at a temperature ranging from about 300° C. to about 600° C.
 2. The process of claim 1 wherein preparing the catalyst composition in an aqueous solution of Ru(NH₃)₆ Cl₃ is used in step a. and a tetrahydrofuran solution of borane is used in step d. 